This invention relates to novel copolymers of keto dicarboxylates useful as complexing agents and detergency builders.
The property possessed by some materials of improving detergency levels of soaps and synthetic detergents and the use of such materials in detergent compositions is known. Such cleaning boosters are called "builders" and such builders permit the attainment of better cleaning performance than is possible when so-called unbuilt compositions are used. The behavior and mechanisms by which builders perform their function are only partially understood. It is known that good builders must be able to sequester most of the calcium and/or magnesium ions in the wash water since these ions are detrimental to the detergency process. However, it is difficult to predict which class of compounds possess useful combinations of builder properties and which compounds do not because of the complex nature of detergency and the countless factors which contribute both to overall performance results and the requirements of environmental acceptability.
Sodium tripolyphosphate (STP) has been found to be a highly efficient cleaning and detergent builder and this compound has been widely used for decades in cleaning and detergent formulations. Indeed, millions of pounds of STP are used each year in cleansing formulations because of its superior builder qualities. However, because of the recent emphasis on removing phosphates from detergent and cleaning compositions for environmental reasons, the detergent and cleaning industry is now looking for materials suitable for use as builders which do not contain phosphorus, and which are environmentally acceptable.
A large number of materials which do not contain phosphorus have been evaluated for use in detergent and cleaning formulations as a builder, but all of these materials suffer one or more disadvantages, usually either poor builder properties or poor biodegradability. As an example, U.S. Pat. No. 3,692,685 discloses salts of oxydisuccinic acid and carboxy methyl oxysuccinic acid as detergent builders and U.S. Pat. No. 3,708,436 discloses a mixture of polymeric maleic anhydride with sodium nitrilotriacetate or STP. Numberous U.S. Patents, such as U.S. Pat. No. 3,704,320, disclose ether carboxylates as detergency builders and several references, such as U.S. Pat. Nos. 3,764,586 and 3,308,067, disclose polymeric, aliphatic polycarboxylic acids having certain specific structural relationships useful as builders.
Despite the advances taught in these and other references in the prior art to find a cleaning and detergency builder which does not contain phosphorus, all of these materials suffer from one or more disadvantages. Of the above mentioned materials, those that are biodegradable are not equivalent to STP in builder performance, and those that are equivalent to STP in builder performance are usually biodegradable only with great difficulty. Inorganic builders other than STP are generally not satisfactory for use as a builder in detergent formulations because of their poor builder properties. Sodium aluminum silicates, commonly known as zeolites, have been proposed for use in detergent formulations since they are able to soften water by removing calcium ions; however, they are not very effective in removing magnesium ions from water. Moreover, it is clear that such water-insoluble, clay-like materials have the potential problem of producing a sediment in the cleaning solution and the resulting waste waters.
Thus, it can be seen that there is a need for a new class of materials with builder properties equivalent to STP, which does not contain phosphorus, which is water-soluble, and which achieves environmental acceptability by being readily biodegradable.
Such a class of materials and its use in detergent compositions has been disclosed in copending application Ser. No. 826,424 filed Aug. 22, 1977 and now abandoned; Ser. No. 826,426 filed Aug. 22, 1977; Ser. No. 826,425 filed Aug. 22, 1977; and Ser. No. 844,566 filed Nov. 17, 1977 and now abandoned. The polymeric acetal carboxylates described in the above applications were tested for sequestration function using the procedures described by Matzner et al in "Organic Builder Salts as Replacements for Sodium Tripolyphosphate", TENSIDE DETERGENTS, 10, No. 3, pages 119-125 (1973) and found to be equivalent or superior to STP. Thus, such polymeric acetal carboxylates were found to be superior detergent builders and were stable under home laundry use conditions, but depolymerized in acid media, making them more readily biodegradable.
Although satisfactory performance was achieved using the polymeric acetal carboxylates disclosed in the above-identified applications, there remains a need for new polymeric carboxylates in detergent formulations for specialized applications. Now, according to the present invention, there is provided a new polymeric carboxylate that is structurally different from the polymeric carboxylates disclosed earlier, that are functional replacements for STP in detergent formulations, and that will undergo biodegradation even more rapidly than the polymeric acetal carboxylates described in the above copending applications.